Recently, there has come to be extensively used an endoscope whereby an affected part or the like within a body cavity can be observed or diagnosed by inserting an elongate insertable part into the body cavity or a curing treatment can be made by using treating tools as required.
Also, there is recently practiced an electronic endoscope (mentioned also as an electronic scope) whereby an image is formed on an imaging surface of a solid state imaging device by objective lenses without using an image guide formed of a fiber bundle and a video signal photoelectrically converted by this solid state imaging device is transmitted to a signal processing means and is color-displayed by a monitor.
Now, in the above mentioned electronic endoscope, when such electric device as a high frequency treating tool is used, a high frequency noise will be output, will be therefore likely to be mixed in an output video signal of the solid state imaging device, will appear on the displaying picture surface and will remarkably reduce the picture quality of the endoscope picture imaged by the solid state imaging device and, in fact, an observation or diagnosis will be no longer able to be made.
In the publication of a U.S. Pat. No. 4,607,621, for the protection from such high frequency noise, there is disclosed a technique wherein an imaging device and video and signal transmitting electric wires are contained in a conductive shield which is electrically connected to a chassis of a video processor and further this chassis is connected to an RF earthing point of a high frequency current source apparatus.
Now, in this technique, as the chasis and shield are connected with each other, a leaking electric current will be likely to flow out of the shield to cause a very dangerous state.